Transmission system

ABSTRACT

In one aspect a transmission system with a transmitter which can be connected to a video source and a receiver linked to the transmitter via at least four circuit pairs, to which receiver a playback device can be connected is provided. Data is usually exchanged digitally between a graphics card in a personal computer and an LCD display module. The personal computer transmits a digital R, G, B video signal to the LCD display module via a special, so-called DVI (Digital Video Interface) cable. This DVI cable is also provided to transmit so-called DDC (Display Data Channel) data, which particularly comprises specification information of the LCD display module. A transmission system is proposed, which simplifies a connection of an LCD display module to a personal computer and with which the DVI cable can be dispensed with.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of German application No.102005027938.4 DE filed Jun. 16, 2005, which is incorporated byreference herein in its entirety.

FIELD OF INVENTION

The invention relates to a transmission system comprising a transmitterwhich can be connected to a video source and a receiver linked to thetransmitter via at least four circuit pairs, to which receiver aplayback device can be connected. Furthermore, the invention relates toa transceiver for a transmission system of this type.

BACKGROUND OF INVENTION

Data is usually exchanged digitally between a graphics card in apersonal computer and an LCD display module. The personal computertransfers digital R, G, B video signals to the LCD display module via aspecial so-called DVI (Digital Video Interface) cable, which comprises acircuit pair for each R, G and B channel. This DVI cable is alsoprovided with further circuit pairs particularly for transmitting a DVIclock signal and for transmitting so-called DDC (Display Data Channel)data. This DDC circuit pair allows the personal computer and the LCDdisplay module to communicate serially, with particularly specificationinformation of the LCD display module, for instance information aboutdata transmission rates, resolution of the LCD display orsynchronization frequency, being transmitted via a data line and a DDCclock signal being transmitted via a clock line.

SUMMARY OF INVENTION

Contrary to DVI cables, so-called CAT5 cables are widely used in officesas standard data cables, which are provided to network data processingdevices. If both DDC and also digital R, G, B video signals are to beable to be transmitted, it is not possible to use this CAT5 cable toconnect an LCD display module to a personal computer.

An object underlying the present invention is to specify a transmissionsystem of the type mentioned at the start, which simplifies a connectionof a playback device to a video source. Furthermore, a transceiver is tobe specified which is suitable for a transmission system of this type.

This object is achieved with regard to the transmission system,receiver, and transmitter specified by the independent claims.

It is advantageous that a CAT5 data cable comprising four circuit pairsand usually already disposed in offices can be used to connect an LCDdisplay module to a graphics card in a personal computer, with both DDCand also digital R, G, B video signals being able to be transmitted viathe economically priced CAT5 cable. The use of an expensive DVI cablecan be dispensed with; in contrast the widely used DVI plugs on theplayback devices and the video sources can continue to be used.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described in more detail below on the basis of anexemplary embodiment with reference to the sole FIGURE of the drawings.The FIGURE of the drawings shows a transmission system with atransceiver.

DETAILED DESCRIPTION OF INVENTION

A transmitter 1 and a receiver 2 are connected to one another via RJ45terminals 3, 4 known per se and via a CAT5 cable 5 likewise known perse, which is usually provided to network data processing devices such asdevices taking the form of servers, printers or personal computers forinstance. The RJ45 terminals 3, 4 are components of devices 1, 2, whichare provided in each instance with further terminals in the form of DVIterminals 6, 7 to connect to a video source (not shown here) and toconnect to a playback device (similarly not shown here). In theexemplary embodiment displayed, the DVI terminal 6 of the transmitter 1is actively connected to a terminal 8 of a personal computercorresponding to this DVI terminal 6 and the DVI terminal 7 of thereceiver 2 is actively connected to a terminal 9 of an LCD displaymodule corresponding to this DVI terminal 7.

The transmitter 1 comprises three circuit pairs 10, 11, 12 fortransmitting digital R, G, B video signals and also a further circuitpair 13 for transmitting a DVI clock signal DVI clock with a first clockfrequency, which can lie between 25 MHz and 165 MHz. Furthermore, thetransmitter 1 is provided with a DDC (Display Data Channel) data lineand a DDC clock line 14, 15, with specification information SDA, forinstance information about data transmission rates, resolution of theLCD display or synchronization frequency or information forparameterizing the LCD display module, being transmitted via the dataline 14, and a DDC clock signal SCL with a second clock frequency of 100KHz being transmitted via a clock line 15. The digital R, G, B videosignals, the DVI clock signal DVI clock and the DDC data signal and DDCclock signal SDA, SCL are transmitted by a graphics card in the personcomputer to the transmitter 1. An amplifier 16 amplifies the DDC datasignal and DDC clock signal SDA, SCL, with a frequency separating filtercomprising a high-pass filter and a low-pass filter 17, 18 superimposingthese DDC signals SDA, SCL onto the DVI clock signal DVI clock.

The transmitter 1 transmits the digital R, G, B video signals to thereceiver 2 via a circuit pair in each instance, as well as the DVI clocksignal DVI clock and the DDC signals SDA, SCL superimposing this DVIclock signal DVI clock via a further circuit pair of the CAT5 cable. Thereceiver 2 is provided with a frequency separating filter comprising alow-pass filter and a high-pass filter 19, 20, which separate the DDCsignals SDA, SCL and the DVI clock signal DVI clock, with the DVI clocksignal DVI clock and the digital R, G, B signals being transmitted tothe DVI terminal 7 and thus to the corresponding DVI terminal 9 of theLCD display module via a cable equalizer 21 and the DDC signals SDA, SCLbeing transmitted respectively thereto via an amplifier 22.

1-3. (canceled)
 4. A transmission system for connecting to a playbackdevice to a video source, comprising: a transmitter connected to thevideo source, the transmitter supplied with a digital R video signal, adigital G video signal, a digital B video signal, a first clock signalsupplied with a first clock frequency, a second clock signal suppliedwith a second clock frequency, a specification signal, and asuperimposer for superimposing the specification signal and the clocksignals; a receiver operatively connected to the transmitter, and to theplayback device, the receiver supplied with a separator for separatingthe specification signal and the clock signals; a first circuit pair forsupplying the specification signal and the clock signals to thereceiver; a second circuit pair for supplying the digital R video to thereceiver; a third circuit pair for supplying the digital G video to thereceiver; and a fourth circuit pair for supplying the digital B video tothe receiver.
 5. The system according to claim 4, wherein the firstclock frequency between 25 MHz and 165 MHz.
 6. The system according toclaim 4, wherein the second clock frequency is 100 KHz.
 7. The systemaccording to claim 4, wherein the separator comprises a low-pass filterand a high-pass filter.
 8. A transmitter for a transmission system forconnecting to a playback device to a video source, the transmittercomprising: a digital R video signal; a digital G video signal; adigital B video signal; a first clock signal supplied with a first clockfrequency supplied to a video source; a second clock signal suppliedwith a second clock frequency; a specification signal; and asuperimposer for superimposing the specification signal and the clocksignals.
 9. The transmitter according to claim 8, wherein the firstclock frequency between 25 MHz and 165 MHz.
 10. The transmitteraccording to claim 8, wherein the second clock frequency is 100 KHz. 11.A receiver for a transmission system for connecting to a playback deviceto a video source, the receiver comprising: a specification signal; afirst clock signal comprising a first clock frequency; a second clocksignal comprising a second clock frequency; the specification signal andthe clock signals supplied via a first circuit pair; a digital R videosupplied via a second circuit pair; a digital G video supplied via athird circuit pair; a digital B video supplied via a fourth circuitpair; and a separating filter for separating the specification signaland the clock signals, wherein the receiver is connected to a playbackdevice.
 12. The system according to claim 11, wherein the separatingfilter comprises a low-pass filter and a high-pass filter.